This invention relates to a method and apparatus for recovering bone and/or oil from animal byproducts and, more particularly, to a method for recovering oil and/or bone from marine byproducts using a relatively low temperature digestion process.
In endproducts produced from animal byproducts, particularly marine byproducts, it may be desirable to remove the oil and/or bone from the byproducts during processing through to the endproduct. This is so because if the endproduct is a feed or food product or additive, the presence of bone will increase ash content which adversely affects nutritional value in some instances. In addition and in many cases with certain marine species, the presence of bone during digestion causes deposits in the digestion tank which are difficult to efficiently remove. Likewise, the presence of oil or a certain amount of oil in an endproduct such as an aquafeed may not be required or may not be required in quantities within the byproducts. The oil removed can be useful and valuable for other purposes.
In our U.S. Pat. No. 6,056,981 (May 2, 2000) and our co-pending U.S. applications Ser. Nos. 09/020,695 and 08/740,004, now U.S. Pat. No. 6,112,699, the contents of which are incorporated herein by reference, there are described certain advantages if the endogenous enzymes and other nutrients in marine related organisms can be used during hydrolysis by applying relatively carefully controlled conditions including lower temperatures so that the naturally occurring enzymes and other nutrients are not destroyed and which will allow the hydrolysis of the organisms to occur. It is contemplated that the natural hydrolysis of a marine organism may be superior to that caused by the artificial adding of exogenous enzymes.
A problem faced by the producers of endproducts using a base of marine byproducts is the removal of oil from the byproducts if the oil or a percentage of the oil is not needed in the endproduct, such as an aquafeed and which oil, when removed, may well be valuable for other purposes.
Many proposals have been made in attempting to efficiently and expediently extract oils from fish wastes. One technique disclosed in 1931 by Leim at the Atlantic Fisheries Experimental Station taught that freezing the livers of cod and pressing the livers thereafter would allow a greater quantity of oil to be obtained than when the livers were steamed resulting in oil coming to the surface and being skimmed therefrom. A further and somewhat unique proposal disclosed in U.S. Pat. No. 2,473,453 (Shropshire) taught that subjecting ground fish liver to a high power compression wave vibration would bring about the release of the oil. These techniques, however, did not contemplate any utility for the product following the removal of the oil.
Steaming the fish livers prior to the removal of oil has been contemplated as being beneficial because of the presence of active enzymes in the livers. These enzymes were seen as destroying the product unless they themselves were destroyed or inactivated. The method of destruction of the enzymes was to heat the product and/or the oils after extraction to relatively higher temperatures thereby inactivating the enzymes or causing xe2x80x9csterilizationxe2x80x9d of the enzymes. This high temperature process is used to the present date because it continues to be considered that the naturally occurring enzymes and other nutrients are not beneficial.
Therefore, present techniques for recovering bone and oil from marine byproducts generally utilise a high temperature process when the oil and/or the bone is separated from the other byproducts. The high temperatures cause destruction of the enzymes and other nutrients in the byproducts which could otherwise be useful as will be described hereafter.
A further problem with existing techniques is that if enzymatic digestion of the marine byproducts is allowed to take place, emulsification of the oils in the byproducts will occur. If oils emulsify, it is considered that the separation of the oils from the product is not possible. It has been found by the applicant, however, that carefully controlling the digestion time and the pH of the product during digestion and by maintaining a relatively low temperature of the product during the digestion step, it is quite possible to extract the oil by appropriate centrifugation following digestion.
According to one aspect of the invention, there is provided a method of removing oil from animal byproduct material comprising the steps of warming the temperature of said animal byproduct material to a temperature of less than 95 deg.C., digesting said animal byproduct material in a first digesting step to substantially liquify said animal byproduct material and centrifuging said animal byproduct material to remove said oil.
According to a further aspect of the invention, there is provided a method of removing bone from marine byproduct material comprising the steps of warming said ground marine byproduct material to a temperature less than 95 deg.C. and deboning said ground marine byproduct material.
According to still yet a further aspect of the invention, there is provided a method for recovering bone and oil from marine byproduct material comprising the steps of grinding said marine byproduct material to reduce the size of solids therein, warming said marine byproduct material to a temperature of less than 70 deg.C., deboning said warmed marine byproduct material, digesting said marine byproduct material to substantially liquify said marine byproduct material and centrifuging said marine byproduct material following said digestion to remove said oil.
According to yet a further aspect of the invention, there is provided products made from any of these methods.